(a) Technical Field
The present invention relates to a method and device for producing a membrane module for a fuel cell. More particularly, it relates to a method and device for producing a membrane module suitable for use in a membrane humidifier for humidifying air in a polymer fuel cell.
(b) Background Art
In general, operation of a polymer fuel cell requires water. Typically, a membrane humidifier that humidifies air supplied to the fuel cell is used for this purpose.
While there are various types of membrane humidifiers, such as a bubbler-type humidifier, an injection-type humidifier, an absorbent-type humidifier, etc., a membrane humidifier having a relatively small volume is used in a fuel cell vehicle due to some space limitations in the fuel cell vehicle. In addition to taking up little space, membrane humidifiers are particularly advantageous because they do not require special power.
As shown in FIG. 1, a membrane humidifier for a fuel cell generally comprises a membrane module 10, a housing 11, and a manifold 12.
Membranes are concentrated in the membrane module 10 and, for example, a plurality of bundles of hollow fiber membranes may be concentrated in the membrane module 10.
The membrane module is generally produced by the following processes.
As shown in FIG. 2, after a case 13 is produced, a potting cap 14 is covered on one side of the case 13, and a desired number of bundles of hollow fiber membranes 15 are put in the case.
Then, a polymer material 16 is injected into both ends of the case 13 to fix the plurality of bundles of hollow fiber membranes in the case 13.
This process is called a potting process.
In the potting process, a urethane material is mainly used as the polymer material.
The potting process uses gravity to fix the bundles of membranes 15 in such a manner that the polymer material 16, which is injected into the case through a resin hole, permeates through the membranes by gravity.
After the potting process, the polymer material is dried, and the potted portion is cut using a cutting device, thereby obtaining a desired membrane module.
Finally, when the housings 11 are put on both sides of the membrane module 10, the production of the membrane humidifier for the fuel cell is completed.
A typical prior art humidifier is one large module in which a plurality of bundles of hollow fiber membranes are received.
However, with such humidifiers, since the plurality of bundles of hollow fiber membranes are received in one large module, the hollow fiber membranes are not uniformly distributed but, rather, are concentrated on one side during the production of the module (see FIG. 3).
FIG. 4 is a schematic diagram showing the configuration of a typical membrane humidifier.
As shown in FIG. 4, the membrane humidifier has a housing 11 provided with a first inlet 17 for introducing dry air and a first outlet 18 for discharging the humidified air, and a membrane module 10 is disposed in the housing 11.
Moreover, a plurality of hollow fiber membranes 15 are received in the membrane module 10.
In the membrane humidifier using the hollow fiber membranes, wet air is supplied from a second inlet 19 and passes through the outside of each hollow fiber membrane 15. Then, the moisture in the wet air is separated by capillary action of the hollow fiber membrane 15, and the separated moisture passes through capillary tubes of the hollow fiber membrane 15 and is condensed. The moisture then moves to the inside of the hollow fiber membrane 15.
The wet air, from which the moisture is separated, moves to the outside of the hollow fiber membrane 15 and is then discharged through a second outlet 20.
Meanwhile, the dry air supplied from the first inlet 17 moves through the inside of the hollow fiber membrane 15.
The moisture separated from the wet air moves to the inside of the hollow fiber membrane 15 to humidify the dry air, and the humidified air is discharged to a fuel cell stack through the first outlet 18.
In the case of the prior art membrane humidifier, the wet air is introduced into the housing 11 through the second inlet 19 to supply moisture to the hollow fiber membranes 15, after which it is then discharged through the second outlet 20.
However, it is difficult for the wet air introduced through the second inlet 19 to penetrate the membrane module in which a plurality of hollow fiber membranes 15 are concentrated.
Moreover, with such membrane humidifiers, the wet air is diffused at a very low speed, which presents further difficulties.
For these reasons, the wet air passing through the outside of the membrane module 10 cannot penetrate the inside of the membrane module which is disposed in the housing 11, but instead mainly flows along the edge.
Further, with such membrane humidifiers, the wet air is diffused into the inside of the membrane module 10 at a very low speed, which significantly decreases the humidification efficiency.
Accordingly, the inside of the membrane module cannot receive sufficient moisture, and the overall efficiency of the membrane humidifier is reduced.
Moreover, in the case of the prior art membrane humidifier, most of the dry air introduced through the first inlet 17 mainly flows through the center of the membrane module 10, and thus the overall efficiency of the membrane humidifier is further reduced.
This is shown from a simulation result in FIG. 5.
Referring to FIG. 5, it can be clearly seen that most of the dry air introduced through the first inlet 17 flows only through the center of the membrane module.
That is, the dry air introduced through the first inlet 17 mainly flows through the center of the membrane module (as indicated by the flow running along the bottom of the Figure). Further, the wet air introduced through the second inlet 19 mainly flows along the edge of the membrane module. As a result, the efficiency of the membrane humidifier is significantly reduced.
The hollow fiber membrane, which is made of a polymer material, accounts for most of the production cost. However, since the prior art membrane humidifier has poor humidification efficiency as mentioned above, an excessive amount of bundles of hollow fiber membranes are used in order to improve humidification performance. As a result, the price of the membrane humidifier increases further. In addition, since a large amount of bundles of hollow fiber membranes are required to increase the humidification performance adequately, the size of the membrane humidifier likewise increases, which causes many difficulties in fitting the membrane humidifier within the limited space of the fuel cell vehicle.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.